fix(prometheus): remove newlines in HELP

pkg/prometheus/parse.go

@@ -3,6 +3,7 @@ package prometheus
 import (
 	"errors"
 	"io"
+	"regexp"
 	"strconv"
 	"strings"
 
@@ -80,6 +81,8 @@ func (p *promTextParser) parseToSeries(text []byte) (Series, error) {
 	return p.series, nil
 }
 
+var reSpace = regexp.MustCompile(`\s+`)
+
 func (p *promTextParser) parseToMetricFamilies(text []byte) (MetricFamilies, error) {
 	p.reset()
 
@@ -101,6 +104,10 @@ func (p *promTextParser) parseToMetricFamilies(text []byte) (MetricFamilies, err
 			name, help := parser.Help()
 			p.setMetricFamilyByName(string(name))
 			p.currMF.help = string(help)
+			if strings.IndexByte(p.currMF.help, '\n') != -1 {
+				// convert multiline to one line because HELP is used as the chart title.
+				p.currMF.help = reSpace.ReplaceAllString(strings.TrimSpace(p.currMF.help), " ")
+			}
 		case textparse.EntryType:
 			name, typ := parser.Type()
 			p.setMetricFamilyByName(string(name))

pkg/prometheus/parse_test.go

@@ -16,6 +16,8 @@ import (
 )
 
 var (
+	dataMultilineHelp, _ = os.ReadFile("testdata/multiline-help.txt")
+
 	dataGaugeMeta, _       = os.ReadFile("testdata/gauge-meta.txt")
 	dataGaugeNoMeta, _     = os.ReadFile("testdata/gauge-no-meta.txt")
 	dataCounterMeta, _     = os.ReadFile("testdata/counter-meta.txt")
@@ -32,6 +34,7 @@ var (
 
 func Test_testParseDataIsValid(t *testing.T) {
 	for name, data := range map[string][]byte{
+		"dataMultilineHelp":   dataMultilineHelp,
 		"dataGaugeMeta":       dataGaugeMeta,
 		"dataGaugeNoMeta":     dataGaugeNoMeta,
 		"dataCounterMeta":     dataCounterMeta,
@@ -51,6 +54,22 @@ func TestPromTextParser_parseToMetricFamilies(t *testing.T) {
 		input []byte
 		want  MetricFamilies
 	}{
+		"Gauge with multiline HELP": {
+			input: dataMultilineHelp,
+			want: MetricFamilies{
+				"test_gauge_metric_1": {
+					name: "test_gauge_metric_1",
+					help: "First line. Second line.",
+					typ:  textparse.MetricTypeGauge,
+					metrics: []Metric{
+						{
+							labels: labels.Labels{{Name: "label1", Value: "value1"}},
+							gauge:  &Gauge{value: 11},
+						},
+					},
+				},
+			},
+		},
 		"Gauge with meta parsed as Gauge": {
 			input: dataGaugeMeta,
 			want: MetricFamilies{

pkg/prometheus/testdata/multiline-help.txt

@@ -0,0 +1,3 @@
+# HELP test_gauge_metric_1 \n			First line.\n			Second line.\n
+# TYPE test_gauge_metric_1 gauge
+test_gauge_metric_1{label1="value1"} 11